1. Field of the Invention
The invention relates to an exhaust gas cooling adapter that forms an exhaust gas flow path that is arranged between an exhaust port that is open to a cylinder head of an internal combustion engine and an exhaust manifold, and through which exhaust gas flows from the exhaust port to the exhaust manifold, and a coolant flow path that is formed inside an adapter wall surrounding this exhaust gas flow path, and that cools the exhaust gas that flows through the exhaust gas flow path.
2. Description of Related Art
Japanese Patent Application Publication No. 2000-291437 (JP-A-2000-291437), Japanese Patent Application Publication No. 2003-227695 (JP-A-2003-227695), Japanese Patent Application Publication No. 2010-190064 (JP-A-2010-190064), and Japanese Patent Application Publication No. 10-317995 (JP-A-10-317995) each describe technology for cooling exhaust gas in order to prevent heat damage to an internal combustion engine exhaust system. JP-A-2000-291437 describes technology in which a recessed portion is formed at a portion where fuel components tend to accumulate, in order to prevent fuel components from accumulating on a wall surface of a passage through which fuel component-containing gas flows. Here, the portion where fuel components tend to accumulate is, for example, a portion where the sectional area of the passage is large and the flow of gas is relatively small, or a wall surface on the inside of a curved passage where the flow of gas is relatively weak, or the like.
JP-A-2003-227695 describes technology in which concavo-convex dimples are formed on an inside wall of a bonnet of an exhaust gas cooling apparatus for a diesel engine. As a result, exhaust gas that flows near the inside wall surface of the bonnet will not peel away from the inside wall of the bonnet, so the flow of exhaust gas will not become stagnant at a portion off to the outside of the center portion, and as a result, PM will not adhere and accumulate.
JP-A-2010-190064 describes technology in which inner fins and dimples are formed on the surface of a tube of an exhaust gas heat exchange portion. These inner fins and dimples make it possible to obtain a turbulence effect on EGR gas, thereby improving the heat transfer coefficient on the EGR gas side, and thus making it possible to improve heat exchange performance.
JP-A-10-317995 describes technology in which an inner wall surface of at least a portion of an exhaust port is formed along the flow direction of exhaust gas. As a result, the amount of generated heat that is recovered by coolant is increased without excessively increasing the load on the internal combustion engine, by further forming fins in the flow direction of the exhaust gas.
Just as with an internal combustion engine to be mounted in a vehicle, in order to save space, it is necessary to curve an exhaust passage in an exhaust gas cooling adapter that is connected to an exhaust port of an internal combustion engine in order to ensure cooling performance of the exhaust gas cooling adapter.
However, when the exhaust passage is curved in this way, the exhaust gas flow may peel away from the inside surface of the exhaust gas passage on the inside of the curve particularly at regions with a high gas flowrate, and as a result, cooling efficiency may end up decreasing. The technology described in JP-A-2000-291437 prevents the accumulation of soot by creating turbulence in the gas flow by forming a recessed portion on the wall surface. In JP-A-2000-291437, peeling of the flow is not described and there is also no mention of heat exchange.
JP-A-2003-227695 describes concavo-convex-shaped dimples provided on a tapered bonnet that increases in diameter in order to deliver exhaust gas to a heat exchange portion. However, the heat exchange portion is not provided at a portion that is curved, and if the heat exchange portion were curved, just how it would be curved is not addressed.
The technology described in JP-A-2010-190064 has inner fins and dimples on the inside of a straight tube, but they not intended to inhibit peeling of the flow at a curved portion of a tube, and a curve in the tube is not addressed.
With the technology described in JP-A-10-317995, fins are formed along the flow, but peeling of the flow at the curved portion of the exhaust port is not able to be dealt with.